1. Field of the Invention
The present invention relates to automobile airbags. More specifically, the present invention relates to a side impact airbag with a thickness that varies over an area of the bag.
2. Description of Related Art
Inflatable airbags enjoy widespread acceptance for use in motor vehicles and are credited with preventing numerous deaths and injuries. Some statistics estimate that the use of frontally-placed airbags reduces the number of fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Other statistics suggest that in a frontal collision, the combination of a seat belt and an airbag can reduce serious chest injuries by 65% and serious head injuries by up to 75%. These numbers and the thousands of prevented injuries they represent demonstrate the life-saving potential of airbags and the need to encourage their use, production, and development.
As a result in part of benefits such as those described above, automakers are now required to install airbags in most new vehicles bound for sale in the United States. Many automobile manufacturers have turned this requirement of implementation of airbag technology into a marketing tool. Enticed by the promise of added safety, vehicle purchasers frequently seek out vehicles with sophisticated airbag systems.
Airbags are often installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the ignition of an inflator. The inflator explosively fills each airbag with expanding gases. The airbags rapidly inflate in front of the driver and passenger to protect them from impact with the steering wheel, dashboard, or windshield.
A modern airbag apparatus may include an electronic control unit (ECU) and one or more airbag modules. The ECU is usually installed in the middle of an automobile, between the passenger and engine compartments. If the vehicle has a driver's side airbag only, the ECU may be mounted in the steering wheel. The ECU includes a sensor that continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor which processes it using an algorithm to determine if the vehicle is in an accident situation.
When the processor determines, based on pre-determined criteria, that the vehicle is in an accident situation, the ECU transmits an electrical current to an initiator in the airbag module. The initiator activates an inflator or gas generator that typically uses compressed gas, solid fuel, or a combination of the two, to rapidly generate a large volume of gas. The gas is channeled to inflate an airbag to absorb the impact of a passenger and thus and prevent injury to the passenger. The airbag then deflates to release the vehicle occupant and prevent asphyxiation in the case of an occupant who has lost consciousness during the collision situation. Some airbags may be fully inflated within 50 thousandths of a second and deflated within two tenths of a second.
An airbag cover, also called a trim cover panel, is generally used to cover a compartment that contains the airbag module. The airbag may be mounted on a steering wheel, dashboard, vehicle door, along a vehicle roof rail, vehicle wall, vehicle floor, or beneath a dashboard. The airbag cover is typically made of a rigid plastic and may be forced open by the pressure from the deploying airbag. In deploying the airbag, it is preferable to retain the airbag cover in at least partial attachment to the vehicle to prevent the airbag cover from flying loose in the passenger compartment. If the airbag cover were allowed to detach and freely move into the passenger compartment, it could cause injury to a passenger.
In an effort to further improve driver and passenger safety, side-impact airbags were developed. These specialized airbags function by providing a buffer between the side of a vehicle and the body of a driver or passenger of the vehicle during accidents in which the side of a vehicle is struck by another vehicle or other object.
In side-impact vehicle accidents, the health and safety of a vehicle occupant is threatened by potential impact of the occupant with the side of the vehicle as well as by possible impingement of the walls of the vehicle into the passenger cabin. In order to protect occupants, it is important to keep the occupant away from the zone of impact located along the side of the vehicle. This helps to dampen the impact to the side of the vehicle, prevent occupant contact with the side of the vehicle, and protect the occupant from injuries cause by deformation of the side of the vehicle and possible impingement of the wall into the passenger cabin.
Further, occupant protection is often maximized when the airbag is contacted by the occupant before the occupant has accelerated through a large distance, and when the thickness of the bag is sufficient to completely or almost completely decelerate the vehicle occupant.
In response to this need, a class of “thorax bags”—airbags specialized to intervene between an occupant and the wall of a vehicle—were developed. This class of airbags was designed to deploy from a compartment within the door, ceiling, or occupant's seat within the vehicle in the instant between the impact of the colliding vehicle and contact of the occupant with the side of the vehicle. This class of airbags includes inflatable curtain airbags, also referred to as “roof-rail airbags.” During a side impact crash event, thorax bags inflate rapidly to cushion the impact of the thorax of an occupant with the wall of the vehicle. Other airbag configurations, such as inflatable curtains, have also been developed to deploy between an occupant and the vehicle walls to similarly cushion the impact of an occupant with an internal surface of a vehicle.
As experience with the manufacture and use of airbags has progressed, the challenges faced by those building and using airbags have become better understood. First, most airbags are designed to rapidly inflate to provide a cushion in front of or alongside an occupant based on a presumption that the occupant will be in a predetermined position. Problems may occur when the occupant is “out of position” in regard to this presumed position.
It was appreciated that in order to provide optimal protection, the bag of this type should be designed to expand to a size sufficient to minimize the distance between the thorax of the occupant and the region of the face of the airbag that the thorax will impact. In such a configuration, the space available to decelerate the thorax would be maximized, while the space available for the thorax to accelerate would be minimized.
In addition, as with other types of airbags, thorax bags must be deployed rapidly in order to be effective. They are most effective when deployed without striking the occupant of the vehicle. Injuries are generally seen where the occupant of the vehicle is in a position unforeseen by the designers of an airbag. These “out-of-position” injuries are important to predict in order to attempt to design a product less prone to cause such injuries.
In addition to the above factors, it is understood in the art that the stored size of an airbag, along with its housing and inflator, must be minimized. This allows the airbag to be accommodated in a wide variety of vehicle designs. It also facilitates installation of the airbag with minimal adaptation of the design of the vehicle and the airbag. Large airbags require larger inflators and housings, and thus there is an incentive to use the smallest effective airbag in a given application.
Further, the operational space requirements of many airbags make installation difficult. The cushion portion of an airbag, which is the portion impacted by a user, must be mounted some distance from a passenger to give the airbag sufficient space to inflate. Because airbags, and especially side impact airbags, must deploy rapidly to adequately protect, they inflate with considerable speed and force. As a result, placement too close to a vehicle occupant increases the risk that the occupant will be injured by the airbag itself. Some compact vehicles simply do not have sufficient interior space to safely accommodate the bulk of airbags such as side impact airbags.
Another difficulty is that many previously known airbags are expensive to produce and install. This difficulty is compounded by the fact that due to variance in the space available in various models of vehicles, the design of the interior of the vehicles themselves, and needed placement of the airbag, airbag designs may need to be modified to be useful in a given line of vehicles. In some cases, the room available to house an airbag assembly, including a housing, the airbag, inflator, and trim panel, may be insufficient to contain a sufficiently large airbag.
Insufficiency in size is determined in side-impact airbags by evaluating the likelihood of a vehicle occupant striking the wall of the vehicle despite the existence of an airbag. Such an event is called a “strikethrough” and may be attributed to insufficient airbag stiffness, thickness, volume, or any combination of these factors. Adjusting any of these factors generally requires increasing the size of the airbag, the inflator, and often the airbag housing itself.
Accordingly, a need exists for an airbag suitable for use as a side-impact thorax airbag, head/thorax airbag, thorax/pelvis airbag, and inflatable curtain that may be adapted in size to minimize the distance between a vehicle occupant and the deployed airbag. It would be an improvement in the art to provide an airbag whose thickness could be varied to allow better deceleration of a vehicle occupant without creating the need to modify the airbag housing or inflator. Such an adjustable volume side-impact airbag is disclosed herein.